10. Promotion of Brian Kidd to Assistant Manager (1991)

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A former Manchester United player and goal scorer in the side's 1968 European Cup final victory, Brian Kidd was brought back to Old Trafford in 1984 to serve as a youth team coach, only four years after retiring as a player.

When Sir Alex Ferguson's then-assistant Archie Knox left the club in 1991, the Scotsman promoted Kidd to the no. 2 role, a position he held for the next seven years.

While playing a key role in the development of the likes of Ryan Giggs, Paul Scholes and David Beckham, Kidd was on hand to oversee a golden period for the club in the mid-90's.

A man born to be an excellent wingman, Kidd now serves as Roberto Mancini's assistant at defending Premier League champions Manchester City.

8. Substitutions in Champions League Final (1999)

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Sir Alex has made quite a few game-changing substitutions while at United, but the most significant have to be the introduction of Ole Gunnar Solskjaer and Teddy Sheringham to the 1999 Champions League final clash with Bayern.

With the side down 1-0 and labouring without key players Roy Keane and Paul Scholes on the pitch, the impact of Fergie's subs effectively won the Red Devils the game.

First, Sheringham neatly turned in a miscued Ryan Giggs shot to level things in stoppage time. Moments later Solskjaer popped up to slam a perfect volley into the roof of the net to leave their German opponents stunned.

7. Signing Cristiano Ronaldo (2003)

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Forgetting the fact that the 2003 signing of Cristiano Ronaldo eventually made the club close to £70 million when he was sold on to Real Madrid in 2009, the Portuguese superstar's impact at the club was immeasurable.

One of the biggest X-factors ever to have played in the Premier League, Ronaldo scored well over 100 goals during his time at Old Trafford.

He helped the club win three consecutive league titles, as well as a precious Champions League trophy in 2008.

Though he is now battling Lionel Messi to be considered the world's greatest player in Spain, make no mistake: His most significant development as a player came under Ferguson in Britain.

5. Mind Games (1996, 2007, 2009)

Though it may be cheating to include a tactic Sir Alex Ferguson has employed many times as a single decision, it is certainly one that has helped define his reputation and success.

The "mind games" the wily Scot has exerted on opposing managers has helped contribute to many a late-season surge.

In 1996, it was Newcastle United's Kevin Keegan cracking. In 2007, it was Arsenal's Arsene Wenger buckling under pressure. While in 2009, it was Liverpool's Rafa Benitez getting riled up by Fergie's very deliberate public comments.

Britain's top managers will no doubt breathe a huge sigh of relief when Sir Alex eventually decides to retire.